In this paper the critical strain energy release rate for T300/913 carbon-epoxy laminated composites has been studied using ANSYS finite element software based on virtual crack closure technique (VCCT). Compact Tension (CT) specimen has been used for numerical analyses and the geometrical dimensions have been extracted from the existing references. The results obtained from the finite element analysis are compared with the existing experimental results in literature. There is good agreement between the critical energy release rate obtained from finite element analysis and the experimental results. Accuracy and simplicity of presented model make it appropriate for predicting the experimental results and improving experimental techniques. The innovation of the present research is the simplicity of the model for simulation of the critical strain energy release rate of the laminated composites. تفاصيل المقالة

The purpose of this paper is to determine mechanical properties of Basalt/Epoxy composites. Test samples were unidirectional composite samples which they are tested according to ASTM D790-96 standard test method by a universal testing machine. Ultimate strength, modulus of elasticity and fracture energy of bending samples are gained. Then pay attention to conditions of unidirectional samples and doing tensile tests on samples, transition coefficients to transfer bending properties to tensile and compressive properties are gained. Using bending test results tensile and compressive properties of samples consist of strength and modulus of elasticity are derived. تفاصيل المقالة

Carbon nanotube (CNT), due to extraordinary mechanical properties, is an effective Stiffener as reinforcement in resin for fabricating of nanocomposites. It is demonstrated by adding a small amount of CNT to the matrix, the elastic modulus of matrix increases remarkably. In this paper, the elastic modulus of CNT reinforced nanocomposites is obtained two-dimensionally using a finite element method (FEM), averaging approach and micromechanical. The obtained results are compared with experimental results that had already been reached by other researchers. It is shown that the experimental results are in acceptable agreement with the results presented in the present paper. Since the utilization of Micromechanics approach is an easier method, this method as used in the present paper can be used to calculate the elastic modulus of CNT reinforced nanocomposites تفاصيل المقالة

This research investigates the effect of the post-cure time on the residual stresses in laminated composites. Laminated composites were made of T300 carbon fibers and epoxy resin. The post-cure process was carried out at the constant temperature of 120 °C for 6 and 12 hours for two specimens. The slitting method was employed to determine through-thickness residual stress distribution of the composite laminates. The experiment results show that the increasing the post-cure time lead to the reduction of maximum residual stress as well as the uniformity of the residual stress distribution in laminated composites. Therefore, increasing the post-cure time is an effective way of reducing the destructive effects of residual stresses in laminated composites. تفاصيل المقالة

In this study, the effective factors on warpage in short fibre reinforced thermoplastic composites has been studied. First of all, the effective factors in manufacturing process were detected and then in order to decrease the number of experiments, the approach of Design of Experiments has been applied. By using micromechanics theory in composites and coefficients of thermal expansion models, a dedicaded code has been used to set up the experimnts. Then the effect of each significant parameter drived and the most effective parameter on warpage phenomenon is detected. At last by using Taguchi's optimization method, warpage of short fibre reinforced thermoplastic composites has been minimized. تفاصيل المقالة

In design and optimization process of laminated composite structures, the number of layers, layer angles, stacking sequence, material types and etc should be specified. Each of aforesaid parameters can be applied as a design variable. In this paper the target is to minimize the weight of laminated composite pin loaded structures. The laminated composite structures are designed based on the load of pin.Pin mounting in laminated composite plates causes stress concentration around the hole of pin. In this research the programming facility of FE software (ANSYS) is used for design and optimization of laminated plate. Constrains of minimization problem is based on Tsai-Wu criterion. The pin loaded plate is divided to two regions: the around of hole and far away from hole. The optimization process is solved concurrently and interactively for two regions. The selected stacking sequences are the quasi isotropic, cross ply and angel ply. The target is to obtain a configuration with accessible number of plies. For this reasom the branch and bound method was used.The obtained results show that the quasi isotropic plate is stronger than cross ply plate and cross ply plate is stronger than angle ply plate. But this order is reversed in a special load. In the other words the cross ply plate is being stronger than quasi isotropic plate in this case. In this paper also effect of geometric parameters over the strength of pin loaded plates are investigated. تفاصيل المقالة

In the slitting method, a small width slit is created incrementally through the thickness of the stressed specimen and the released strains in each increment are recorded by a strain gauge. Compliance coefficients relate the measured strains to the residual stresses. This paper investigates the important parameters influencing the calculation of compliance coefficients for isotropic plates and laminated composites by finite element analysis. First, the process of slitting in isotropic materials is simulated using two and three-dimensional finite element models. The results show complete agreement between these two models. Calculation of average strain at the strain gauge location is necessary for the calculation of compliance coefficients. For this purpose, strain-based and displacement-based methods are used. In addition, the effect of slit width on compliance coefficients is checked. Then, released strains by strain gauges with different gauge-lengths are compared with each other. The results show that the strain gauges with smaller gauge-lengths can record higher values of released strain and consequently increase the precision of measurements. Lastly, compliance coefficients for two glass/epoxy and carbon/epoxy laminates are calculated using the proposed three-dimensional model. تفاصيل المقالة

In this study, a novel numerical method is proposed for determination of mode-I interlaminar fracture toughness, GIc, in multi-directional (MD) double cantilever beam (DCB) specimens using fracture properties of unidirectional DCB specimens. Two factors, β and Dcare defined to minimize the undesirable effects on strain energy release rate. β describes the difference between maximum and average of SERR along the delamination front. Dcshows the bending-bending coupling of laminated composites. β and Dcfactors are not independent factors because both of them affect on distribution of SERR. As a result, by 3D modeling of DCB specimen in ANSYS software, limitation of β is determined so that the fracture toughness of MD DCB specimen with 0//0 interface can be predicted from toughness of unidirectional DCB specimen. Numerical results shows that fracture toughness predicted with the proposed approach is in good agreement with available experiments in the literature for β < 20%. تفاصيل المقالة